Abstract

For stratified samples where material is being uniformly deposited or removed at a known rate, the dielectric response εo of the outermost few Å is exactly determinable from the value and thickness derivative of the complex reflectance without any knowledge of the underlying structure. For ellipsometric data the equivalent analysis is not exact, but a common‐pseudosubstrate approximation is developed, that in applications to semiconductor crystal growth, is accurate to better than 0.1%.